1. Technical Field
This invention relates generally to the field of image processing systems and, more particularly, to an apparatus and method for displaying a portion of a spherical image field that is created from one or two 180 degree or greater hemispherical images, generated from either a still photograph, rendered image, or a motion picture or video input. Specifically, the present invention relates to a system where desired portions of one or two 180 degree images are used to create a dewarped and perspective-corrected window into the image or images. The method involves the use of a mathematical transformation to remove distortion associated with a fisheye or other wide angle lens, correct perspective associated with changes in the direction of view, and select which hemisphere of the original images a given picture element resides. In addition, the method creates an environment that totally fills a spherical environment resulting in no boundaries, thus, creating a so-called immersive image viewing experience. It does so preferably by combining two images into a complete sphere (i.e. permitting continuous navigation without any boundaries in the spherical image). The image can be composed of a single half image with the second half composed of the mirror image of the first image or a second hemispherical image that is captured by a camera directed in the opposite direction of the first. The preferred system includes a computational device for implementation of the corrective algorithms (personal computer, TV settop device, or hardware for computation of the transformations), an input device (a computer mouse, touchscreen, keyboard or other input device), a display monitor (a television, computer monitor or other display device), and image data that is collected from either one or two 180 degree or greater (for example, fisheye) images that are still, rendered, motion or video.
2. Background Art
The discussion of the background art related to the invention described herein relates to immersive image viewing. "Immersive image viewing" as used in the context of this application means the concept of permitting a viewer to be totally immersed in an image by allowing the user, for example, to focus on a particular object in an object plane and selectively having that image displayed in an image plane without warping or distortion as if the user had seen the object with his or her eyes.
One goal of the present invention is to create an immersive image environment and another to provide a means for the user to experience such a totally immersive image environment, providing full freedom in the viewing direction inside of a complete sphere composed of one or two combined hemispherical images. As a result, there are no bounds on the user's freedom to view in any direction.
Some virtual reality approaches have been developed that use multiple images to capture a cylindrical representation of an environment from a composition of numerous still images (Apple Computer's QuickTimeVR) or a cylindrical image from a mechanized panoramic camera (Microsoft Corporation's Surround). Apple's QuickTimeVR may be described by Chen et al., U.S. Pat. No. 5,396,583. These methods suffer from at least two constraints: 1) the capture of the image requires precise methods and equipment not amenable to consumer application, and 2) the playback to the user is limited by the cylindrical composition providing a 360 degree panorama all the way around but a limited tilt in the vertical (up/down) direction.
In parent U.S. Pat. No. 5,185,667, an approach is described which uses a single image and allows navigations about the single image. The described method involves the capture of a single wide angle image (not a complete spherical image) and is thus limited in the effect on the user by having limits set at the edge of the wide angle field of view, thus constraining the user to a region of view direction.
Other methods (for example, a system under development at Minds Eye View of Troy, New York) are expected to use image projection to create alternative perspectives from dual fisheye images and process these images in a manual manner to create a composite of images that can be videotaped to create the sense of movement through environments. These alternative perspectives are combined, frame by frame, offline and, consequently, due to the computational complexity of the approach, real-time interaction has not been possible. This approach offers no interactive potential to allow the user to direct his own view and lacks accuracy at the seam between perspectives to automatically combine images without manual touch up (editing) of the original fisheye images.
Approximations based on bilinear interpolation (Tararine, U.S. Pat. No. 5,048,102) as applied to a distorted image allow for computational speed increases, but are limited to a fixed viewing perspective and to a single source of input data (hemisphere) instead of an entire sphere of input for total immersion which requires additional logic to determine from which source to obtain the information.
Still other approaches provide a higher resolution in the video domain by combining numerous narrow angle imaging devices in an approximately seamless manner (McCutchen, U.S. Pat. No. 5,023,725), but these devices require the combination of numerous signals into a composite image and also are only piecewise continuous having issues (distortions) at the intersection of various sensors (parallax).